1. Field of the Invention
This invention relates to a chainless haulage system for pulling various mining machines along a long wall coal mining face.
2. Description of the Prior Art
Coal getting machines for long wall mining have historically been pulled along the coal seam face by means of a chain stretched along the entire length of the long wall face. However, the energy stored by a machine haulage chain under tension is a potential danger that has tended to increase in recent years with the trend towards multi-machine working and the use of higher horse power machines on the face. Although devices have been developed to limit tensions in chains and to release these chains safely in the event of machine stalling, nevertheless the severity of the mining operation has resulted in breakage of the chain which has produced serious injury to machine operators and distruction of mining equipment. Accordingly, in recent years effort has been directed to developing an alternate means of driving a power loader along the mine face completely eliminating the haulage chain previously employed.
In recent years therefore several chainless haulage systems have been developed to pull and track coal getting machines off the line of face conveyor pan sections. Several of this type chainless haulage systems are described by Braisby et al., "Review of Chainless Haulage Systems" Colliery Gardian, November, 1976, pages 577-586. For the most part, however, recent chainless haulage systems are based on some form of the rack and pinion principle. Therefore these systems are inherently pitch sensitive and unable to accommodate misalignment of the element forming the "rack". Also, the recently developed systems of the prior art are based on "push-pull" cylinders, and require good alignment of guide rails associated with these systems.
Examples of recently developed mining haulage systems can also be found in U.S. Pat. Nos. 3,954,300; 4,006,937; 4,025,120; and 4,055,367.